Liquid crystal displays (LCDs) are commonly used as display devices for compact electronic apparatuses. This is not only because they provide good quality images with little power consumption, but also because they are very thin.
Referring to FIG. 5, a typical liquid crystal display 500 includes a liquid crystal panel 510, a backlight module 520, a plastic frame 530, a flexible printed circuit 540, a bottom tray 550, a first anisotropic conductive film (not shown), a second anisotropic conductive film (not shown), and a printed circuit board (not shown). The bottom tray 550 defines a gap 551. The liquid crystal panel 510 includes a first substrate 511, a second substrate 512 generally facing the first substrate 511, a liquid crystal layer 513 sandwiched between the first substrate 511 and the second substrate 512, and a driving integrated circuit (IC) 514. The second substrate 512 includes a main portion 5121 and an extending portion 5122. The main portion 5121 of the second substrate 512 is attached with the first substrate 511. The extending portion 5122 extends outward from the main portion 5121. A plurality of conductive lines (not labeled) are disposed on an upper surface of the extending portion 5122. The driving IC 514 is electrically connected with the conductive lines via the first anisotropic conductive film.
The backlight module 520 includes a reflective film 521, a light guide plate 522, an optical film assembly 523, a light-blocking tape 524, and a plurality of light sources 525. The reflective film 521, the light guide plate 522 and the optical film assembly 523 are arranged in that order from bottom to top. The light guide plate 522 includes a light incident surface 5221. The light sources 525 are located adjacent to the light incident surface 5221 of the light guide plate 522. The light sources 525 can be point light sources such as light emitting diodes.
The light-blocking tape 524 includes a first portion 5241, and a second portion 5242 integrated with the first portion 5241. The first portion 5241 is frame-shaped. The second portion 5242 is strip-shaped. The first portion 5241 is configured for making peripheral edges of the optical film assembly 523 adhere to peripheral edges of the main portion 5121 of the second substrate 512, and for preventing light beams from transmitting through the peripheral edges of the main portion 5121 of the second substrate 512. The second portion 5242 is attached to a lower surface of the extending portion 5122 of the second substrate 512 for shielding light beams.
The flexible printed circuit 540 includes a panel driving end 541, a light source driving end 542, and an external connecting end 543. The panel driving end 541 is electrically connected with the conductive lines on the extending portion 5122 of the second substrate 512 via the second anisotropic conductive film. Because the conductive lines are also electrically connected with the driving IC 514, the panel driving end 541 of the flexible printed circuit 540 is thus electrically connected with the driving IC 514. The panel driving end 541 provides a plurality of panel driving signals to the driving IC 514 so that the liquid crystal panel 510 displays images.
Referring also to FIG. 6 and FIG. 7, the plastic frame 530 and the bottom tray 550 cooperatively form an accommodating space to accommodate the reflective film 521, the light guide plate 522, the optical film assembly 523, the light-blocking tape 524 and the liquid crystal panel 510, in that order from bottom to top. The flexible printed circuit 540 is bent such that the light source driving end 542 of the flexible printed circuit 540 is sandwiched between the light sources 525 and the bottom tray 550. The light source driving end 542 is electrically connected with the light sources 525, and is configured to provide working voltages for the light sources 525. The external connecting end 543 extends through the gap 551 of the bottom tray 550, and is welded on the printed circuit board for receiving working voltages of the liquid crystal panel 510 and the light sources 525.
As described above, the flexible printed circuit 540 is bent such that the light source driving end 542 of the flexible printed circuit 540 is sandwiched between the light sources 525 and the bottom tray 550. Since the flexible printed circuit 540 is bent and under tension, the light source driving end 542 thereof occasionally moves downwardly toward the bottom tray 550. When this happens, the light sources 525 typically do not face the light incident surface 5221 of the light guide plate 522 properly. Accordingly, some of the light beams emitted by the light sources 525 leak out and cannot reach the light incident surface 5221 of the light guide plate 522. Thus a light utilization ratio of the liquid crystal display 500 may be unsatisfactorily low.
What is needed, therefore, is a liquid crystal display that can overcome the above-described deficiencies.